Earth Processes and the Coastline

Name ________________________________________________________ Date___________ Period _____________
Earth Processes and the Coastline
Beach Formation
1. The appearance of a beach depends on what two most important factors:
a) The amount of sediment moved to the coast by the river
b)The amount of wave energy hitting the shore
2. Beaches are found near the mouth of a river where sediments are deposited.
3. A beach will form when the amount of sediments supplied by river is in the balance with the erosion energy
of the ocean waves.
A Naturally Changing Coastline
4. When sediment supple from the river is much more that the ocean waves can erode, a delta will form. It
forms when deposition is greater that erosion.
5. Deltas are formed on coastlines when large rivers.
If a coastline erodes and moves inland, a cliff can form from any nearby high land. It forms when erosion is
greater that deposition.
Longshore Current
7. Sand along a beach is pushed across the shore as well as in and out.
8. The longshore current, which is a result of waves hitting the beach at an angle, is a stream of water in the
ocean that runs parallel to the shore and moves sand across the fence of the beach.
9. Humans can cause environmental impacts along the beach when they build there.
10. Most of the time, construction interrupts the longshore current, causing excessive deposition of sand near
the structure.
11. Draw picture from p. C-46
Longshore Current
Managing Earth Processes
12. One way to protect the beach from deposition is to dig up the sand and move it to another location, which
is called dredging.
13. A jetty is a rock structure built perpendicular to the shore that prevents unwanted deposition by collecting
sand on one side of it before it reaches the structure.
14. Draw Figure 2: Jetty on p. C-47
Example of Jetty
15. Erosion is also a problem we face when building on the shore because the force of the ocean waves.
16. One way to slow down the erosion is the reduce the energy of the waves by using a breakwater
17. A breakwater is a rock structure that is built parallel to the shore
18. Draw Figure 3: Breakwater on p. C-47
Example of Breakwater
19. Sometime piles of rock or seawalls are built right up against the cliff or shoreline
20. Ocean waves hit the structure instead of the cliff, which reduces the amount of erosion.
21. Choose a method that you would use to control either erosion or deposition on the coastline. For the
method you choose, describe both an advantage and a disadvantage of its use.
Advantages and Disadvantages of Erosion Mitigation Methods
Mitigation Method
 Protects beach from
 A lot of work
excessive deposition
 Can expose contaminated
 Can make land less stable
 Can help avoid the buildup
 Will increase deposition on
of deposition
the up stream side of the
 Can prevent a harbor from
filling with sediment
 Reduces the energy of the
 Slows down longshore
current so sediments in
current are deposited
 Slows erosion
between the breakwater
and beach
Seawall (or riptide)
 Waves hit structure instead
 Erosion around sea wall
of cliff or shoreline
 Reduces wave erosion